IBM IOS Developer Interview Questions and Answers

Classes and structures are both used to define custom data types, but they have some key differences.

• Classes are reference types, while structures are value types.

• Classes support inheritance, while structures do not.

• Classes have deinitializers, while structures do not.

• Classes have reference counting for memory management, while structures do not.

• Classes can have optional property types, while structures cannot.

Retain cycle is a memory management issue where objects reference each other and cannot be released. It can be avoided by using weak or unowned references.

• Retain cycle occurs when two or more objects hold strong references to each other.

• To avoid retain cycle, use weak or unowned references instead of strong references.

• Weak references do not increase the reference count of an object and automatically become nil when the...read more

Opinion binding is a legal doctrine that requires judges to follow the decisions of higher courts in similar cases.

• Opinion binding is also known as stare decisis.

• It helps to ensure consistency and predictability in the legal system.

• For example, if a higher court has already ruled that a certain law is unconstitutional, lower courts must follow that ruling in similar cases.

• Opinion binding can be controversial, as it can...read more

GCD and Operation Queues are both used for concurrent programming in iOS, but differ in their approach.

• GCD is a C-based API that uses a thread pool model for concurrency.

• Operation Queues are built on top of GCD and provide a higher-level abstraction for concurrency.

• GCD is best for simple, lightweight tasks, while Operation Queues are better for more complex tasks with dependencies.

• GCD uses blocks for task execution, wh...read more

The life cycle of iOS applications refers to the stages an app goes through from launch to termination.

• The app is launched by the user or system

• The app enters the foreground and becomes active

• The app can be sent to the background or suspended

• The app can be terminated by the user or system

• The app can be resumed from the background or suspended state

• The app can receive memory warnings and handle them appropriately

The UIViewController life cycle consists of several stages that occur when the view controller is loaded and unloaded.

• viewDidLoad() - called when the view controller's view is loaded into memory

• viewWillAppear() - called just before the view appears on the screen

• viewDidAppear() - called just after the view appears on the screen

• viewWillDisappear() - called just before the view disappears from the screen

• viewDidDisappear()...read more